Automatically controlled pressure flow suction flatbox for paper-making machine



Aug. 18, 1966 J. T. CRIBBEN AUTOMATICALLY CONTROLLED PRESSURE FLOW SUCTION FLATBOX FOR PAPERMAKING MACHINE Filed Aug. 2, 1963 5 Sheets-meet 1 INVENTOR. damasfihvas Cr/bfie/r BY w AT RNEYS Aug. 16, 1966 J. T. CRIBBEN AUTOMATICALLY CONTROLLED PRESSURE FLOW SUCTION FLATBOX FOR PAPERMAKING MACHINE 5 Sheets-5neet 2 Filed Aug. 2, 1963 I NVENTOR.

dimes 7500756 Cr/Zbe/I A TTORNEYS Aug. 16, 1966 J T. CRIBBEN 3,266,975

AUTOMATICALLY CONRROLLED PRESSURE FLOW SUCTION FLATBOX FOR PAPERMAKING MACHINE Filed Aug. 2, 1965 5 Sheets-5neet 5 I NVENTOR.

James 2720 (Zz'bezz A ORNEYS United States Patent 3 266,975 AUTOMATHCALLY CON'IROLLED PRESSURE FLQW SUCTION FLATBOX FOR PAPER- MAKING MACHINE James Thomas Cribben, Janesville, Wis., assignor to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Aug. 2, 1963, Ser. No. 2%,653 7 Claims. (Cl. 162-252) This invention relates to suction regulating means, and more particularly, to an arrangement for maintaining stable conditions in a suction chamber in a device such as a paper machine.

Although the instant invention may have use in a number of fields, it is particularly useful in the art of paper making. The invention relates to the regulation of pressure in a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto, such as a flatbox operating beneath the forming wire of a paper machine, a suction gland in a suction press roll or suction couch roll in a paper machine (in whch case the suction gland is exposed to the perforate roll shell), or even in some instances savealls operating in close running relation with a traveling perforate surface such as the Fourdrinier wire or a perforate suction roll shell through which water enters into the saveall. The instant invention is, however, primarily concerned with obtaining the advantages of regulating pressure in a suction flatbox. As will be appreciated, conditions in the stock passing over a suction flatbox will vary. Some present-day devices are known which attempt to compensate for such variation, and typical examples thereof are disclosed in Beachler US. Patent No. 3,024,839, owned by the assignee of the instant application, and Bratton US. Patent No. 2,608,913.

The instant invention is particularly concerned with control of the pressure in the suction box as well as drainage of the water therefrom. In present-day machines, the width or cross-machine dimension is very substantial and drainage of water from suction chambers such as the flatbox is ordinarily carried out through a conventional conduit connection at one side of the machine and, therefore, one end of the suction box. Particularly, for example, in the case of wet end suction boxes where large amounts of water tend to create a comparatively high water level in the suction boxes, problems may be created by such a substantially high pond depth when flowing in an open channel with vacuum applied along the top surface of the pond in the suction box. The principal difficulty is that there may be a tendency for uneven pressure differentials across the forming wire caused by interference with the regulation of the suction pressure in the suction box due to such high pond levels. It is particularly important to maintain a substantially uniform pressure differential across the forming wire at this stage in the machine, and surging of substantial amounts of water within the suction box may cause nonuniform (subatmospheric) pressure in the cross-machine direction from the front to the back side of the machine, where the water is actually removed from the suction box. In fact, in severe flooding of the suction box the subatmospheric pressure may be lost completely beneath the wire in certain areas with resultant damage or destruction of the web forming on the wire.

It will also be appreciated that under certain operating conditions, there are limitations in the subatmospheric pressure range that may be applied to the interior of the suction box beneath the wire. As a consequence, when nominal subatmospheric pressures are used in the suction box (which are normally used when large amounts of water are removed from a wet sheet), the suction box is not capable of disposing of the extracted water at a rate ice greater than (or sometines even equal to) the rate at which water enters the box. Flooding may then result in the suction box, with complete loss of vacuum and substantial destruction of the sheet carried by the wire over the flooded box.

The instant invention affords a unique concept of pressure control and maintenance of pressure differentials in a suction chamber system. In essence, the instant invention provides for the concept of maintaining a predetermined desired pressure differential across a perforate wall or member, such as the suction box top with the wire thereon, so that drainage of liquid through the perforate member is carried out to the extent and in the manner desired. In addition, the instant invention provides for the maintenance of a second pressure differential in desired, predetermined manner between the level of liquid in the suction chamber and a vacuum source connected directly or indirectly to the suction chamber beloW the liquid level therein. This latter pressure differential serves to maintain a predetermined desired level in the suction chamber and control the drainage rate therefrom to the extent necessary to maintain such predetermined level.

Although a number of embodiments of the instant invention will be described in detail hereinafter, it will be appreciated that one aspect of the instant invention provides for the maintenance of a predetermined pressure on the liquid level in the suction chamber, and a second predetermined and preferably much lower pressure in a receptacle outside of the suction chamber receiving liquid from beneath the liquid level in the suction chamber. In prior art devices, the vacuum header was ordinarily connected to the drainage system for suction boxes so that water and air were both drawn through conduits at the end of the suction box, with the water and air being separated in a conventional drop leg leading to a seal pit. In this arrangement the effective pressure on the liquid in the suction box was substantially the same as the effective pressure on the liquid in the drop leg and drainage control or regulation was thus limited. In the instant device there is maintained a controllable, significant pressure differential between the liquid level in the suction box and that in a conventional drop leg or other drainage receptacle outside of the suction chamber by the use of a conduit draining liquid from below the level in the suction box to such receptacle plus a separate and independent conduit communicating with the suction box above the liquid level therein and provided with separately controllable pressure regulating means. In the typical suction box operation of a paper machine, such pressure regulating means will maintain a desired subatmospheric pressure beneath the perforate box top for suitable water drainage, while maintaining the same subatmospheric pressure on the liquid level in the suction box. A substantially lower and readily controlled pressure may thus be maintained in the separate liquid receptacle so that the subatmospheric pressure against the liquid level in the suction box will function to drive the liquid out of the suction box, through the drain conduit beneath the liquid level, and into such receptacle operating at the substantially lower subatmospheric pressure.

It is, therefore, an important object of the instant invention to provide an improvement in pressure regulation and control in suction chambers as well as drainage regulation and control therefor.

It is a further object of the instant invention to provide a pressure differential drainage control for removing liquid from a suction chamber.

Yet another object of the instant invention is to provide apparatus for affording uniform cross-machine pressure differentials across a paper machine forming Wire.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof.

On the drawings:

FIGURE 1 is an elevational fragmentary view of the drainage and of a suction box in a paper machine, with parts broken away and parts shown in section;

FIGURE 2 is a. detail view taken substantially along the line IIII of FIGURE 1;

FIGURE 3 is an elevational, partially diagrammatic view showing an alternative valve arrangement for use in the embodiment of FIGURE 1;

FIGURES 4, 5 and 6 are essentially diagrammatic views showing other embodiments of the instant invention and control connections therefor;

FIGURE 7 is a fragmentary, elevational, partially diagrammatic view of another embodiment of the instant invention; and

FIGURE 8 is a diagrammatic view of the suction box arrangement of FIGURE 1 illustrating a plurality of first chambers operatively connected to a single second chamber.

As shown on the drawings:

In FIGURE 1, the letter W indicates generally the back edge of the traveling forming wire with stock thereon, traveling over a conventional perforate suction box top 10 secured with conventional means 11 to the top 12 of a suction box chamber indicated generally at A. A conventional adjustable suction box top seal aligned with the wire edge is indicated generally at 13, with the threaded adjustable means indicated at 14, and such elements need not be described in further detail herein. The suction box chamber A is of course provided with transverse walls, only one 14 of which is shown in FIG- URE 1, a bottom wall 15 and an end wall assembly indicatcd generally at 16, which will be described in greater detail hereinafter. It will be noted that the water and air pass through the perforations indicated at 1% in the perforate box top It and separate in the suction chamber A so as to maintain a liquid level L-l in the chamber A.

A drawolf line or conduit indicated generally at 29 is provided with certain conventional features as a drop leg 21 leading to a seal pit (not shown) and a top air exhaust line 22 leading to a vacuum or suction header 23 which is, of course, connected to a conventional exhaust pump for maintenance of a source of vacuum in the line 22 and header 23. A control valve indicated diagrammatically at 24 is also provided for regulation of the vacuum in the drawoff line 29, which is regulation of the subatmospheric pressure in the air space A4. in the drawoif conduit 26 above the liquid L-2 therein, which results from the continuous exhausting of air escaping from the liquid L-2 and being drawn into the suction header 23.

The conduit 20, however, is connected to the suction chamber A solely through an opening indicated at 25 in the end wall 16 that is beneath the liquid level Ll in the pond or pool of liquid in the suction chamber A. It will thus be seen that the only air escaping from the suction chamber A into the drawoff conduit 26 is that entrapped in the liquid and carried through the opening 25 with the flowing stream of liquid L2. Such escaping air from the flowing liquid L2 will affect the pressure in the air space A1 above the liquid L2 in the drawoff conduit 29, but such pressure is effectively controlled also via the valve 24 and the suction header 23 so that subatmospheric pressure may be maintained in the air space A-l above the liquid L-2 in the drawoff chamber 29 that is substantially different from the pressure in the air space above the liquid level L-lt in the suction chamber A.

Referring briefly to FIGURE 2, it will be seen that FIGURE 2 shows the adjustable valve means for the end opening 25 and the end wall 16. In FIGURE 2, it will be seen that a vertically adjustable dam or gate 26 is provided with side rubber seals 26a and 26b which sealingly and slidably engage the transverse suction box walls indicated at 14 and 14a for movement toward and away from the bottom wall 15 to control the size of the opening 25 and thus control the flowof liquid out of the suction chamber A and into the drain or drawoff conduit 2%. Vertical adjustment of the gate 26 is afforded by a pair of threaded adjusting rods 27, 27 rotatably received by sleeves 28, 23 movable longitudinally with the rods 27, 27 and secured to the gate 26 in rigid assembly. The rods 27, 27 are received in threaded sleeves 29, 29 mounted in rigid assembly on the chamber roof portion 12.

The actual body 16a of the end wall indicated generally at 16 is provided with an upper aperture 30, and a lower aperture 31 generally aligned with the control aperture 25 provided by the gate 26 which sealingly engages a rubber seal 32 in a channel 16b extending the full width of the end wall 16. The end wall 16 is also provided with a complete peripheral channel 160 with a peripheral rubber seal 33 mounted therein for sealing engagement with an end flange 34.

The end wall 16 is secured to the flange 34 by conventional means for effecting the desired seal so that the upper opening is completely separate and apart fromthe lower opening 31 in the end wall 16. Air drawn into the suction chamber A is drawn through the upper opening 30 above the level L-l and into a separate chamber A-2 which chamber A-2 is in direct gaseous communication with the perforate box top 10 and the top of the liquid level L-1 in the chamber A. The chamber A-Z is separated from the lower vacuum chamber A1 by virtue of the gas seal afforded by water in the chamber A at the level L-l and also by an air tight bulkhead 35 which is actually a continuation of the roof of the drawoif chamber 20. A sight glass window 36 is secured by conventional means to the end wall 37 of the vacuum chamber conduit A-Z, which is exhausted through a conventional air exhaust line 38 secured by a conventional flange mounting 39 to the top of the chamber A--2 and feeding through a control valve 49 to a second vacuum header 41.

In manual operation of the embodiment of FIGURES 1 and 2, the operator may observe through the sight glass window 36 the level L-I in the suction box chamber A. If a change in the operation of the paper machine takes place such that the level Lll appears to be rising, then the operator can manually adjust the rods 27, 27 so as to open the gate 26 slightly to accommodate faster liquid drawotf in the line 20. If a more rapid change is required the operator can, of course, either open the vacuum control valve 25 wider or close the vacuum control valve slightly so as to increase the pressure differential between the vacuum chamber A-ll and the vacuum chamber A2 (which is maintained at substantially the pressure of the air above the liquid level L4. in the suction chamber A). The pressure in the vacuum chamber or conduit A2 is preferably indicated in a conventional pressure gauge G connected thereto, and this pressure is ordinarily controlled by the operator so as to maintain the desired pressure differential across the suction box top 10, which is exposed to substantially atmospheric pressure on the wire side. The subatmospheric pressure in the lower vacuum chamber A-l, however, can be regulated to a very low pressure so as to obtain the desired pressure differential between the chambers A2 and A-1 to cause the desired rate of drainage through the gate valve aperture 25.

Referring to FIGURE 3, it will be seen that elements corresponding to those shown in FIGURE 1 are indicated by the same reference numerals in the series. The upper and lower vacuum chambers A102 and A4101 are, of course, maintained at the desired pressure differential in the manner hereinbefore described, and the liquid level L1ll1 is maintained in the suction chamber A-MEQ by this pressure difierential as well as control of a damper valve 150 swingably mounted from a seal corresponding to the seal provided by the rubber strip 32 in FIGURE 1, and the damper 150 is adjustably moved by a conventional threaded adjusting rod 151 mounted in a threaded sleeve 152 and manually operated by a handle 153 in conventional manner.

Referring now to FIGURE 4, it will be seen that elements corresponding to those already described in FIG- URE l are designated by the same reference numerals in the 200 series. The liquid outlet 225 is here controlled by a damper valve 250 comparable to the valve 150 of FIGURE 3, except that it is actuated by a rod 255 longitudinally movable in a seal 256 by means of a conventional motor such as a pneumatic motor 257 which moves the rod 255 longitudinally to the left or to the right, selectively, and responds to a control signal received through the control line 258 which is actuated through a conventional control box 259 that is in turn actuated by a signal from a control line 260 received from conventional level sensing means indicated at 261 in the suction chamber A-200 for sensing the level therein L-201. Although any level sensing means 261 of conventional structure and function may be used, the unit shown here diagrammatically comprises spaced sensors X and Y. In operation, the level L201 is maintained generally between the spaced level sensors X and Y.

If the level L-201 rises so as to give a signal to the level sensor X, then the signal is passed through the control line 260 to the control box 259 where it is converted to a pneumatic signal in the control line 258 which in turn actuates the pneumatic motor 257 to urge the control rod 250 so that the level will go down in the suction chamber A-200. Alternatively, if the level L-201 drops down below the level sensing device Y, a different signal is transmitted to the control box 259 and the rod 255 is ultimately actuated in the opposite direction.

It will be seen also from FIGURE 4 that the liquid stream L-202 flowing through the aperture 225 beneath the level L-201 carries a certain amount of entrained or trapped air or gas which is released in the overhead portion of the chamber A-201, and the liquid itself flows into a conventional dropleg 270 whose bottom is submerged below the level L-203 in a conventional seal pit 271. Because of the reduced pressure in the drawoff chamber A201, atmospheric pressure against the seal pit level L-203 effectively maintains a substantially higher level L-204 for a continuously forming liquid pool in the dropleg 270 (and, of course, outside of the suction box A-200).

It will be appreciated that the instant device maintains a controlled, regulated and predetermined pressure differential between the gases acting against the level L-201 in the suction chamber A-200 and this liquid level L204 on the continuously forming il iquid (white water) pool in the dropleg 270. This pressure differential permits the selected driving of the liquid from the suction box A400, whereas in the prior art the air from above what is now the level L-201 in the suction box A-200 would also travel out the conventional outlet (which would be larger in size than the present outlet 225) and would effectively maintain the same pressures on the continuously forming white water pool at the level L-204 here indicated. In the instant device, however, the pressure differentials between t-he levels L-201 and L204 are maintained by separate and independent sources of vacuum 223 and 241, separately and independently controlled by the control valves 224 and 240, respectively. In the device of FIGURE 4 the control valves 224 and 240 are indicated as being set manually and the automatic control is provided only in connection with the damper valve 250 which is moved in response to signals from the level sensing device 261. It will be appreciated that the separate suction headers 223 and 241 are maintained at different subatmospheric pressures, preferably, but they may be connected to a common exhaust pump indicated at P via ex-haust lines 272 and 273 with additional control valves 274 and 275 therein feeding into a conventional separator 276 with a valve drawoif 277 for entrained water. Essentially, however, the control valves 224 and 240 positioned, respectively, between the vacuum sources 223 and 241 and the first and second drawoif conduits A-201 and A-202 maintains the overall desired pressure differentials, which include not only the pressure differential between the levels L201 and L-204 in control of drainage but also the pressure differential between the ambient atmosphere urged against the stock on the forming wire and the pressure at the level L-201 (which is in effect the pressure differential across the perforated wall in the suction box A'200).

Referring to FIGURE 5, it will be seen that a somewhat different control arrangement is employed, but elements corresponding to the same elements as those previously disclosed herein are given the same reference numeral-s in the 300 series. In FIGURE 5, the first and second dra woif conduits A-301 and A-302 are connected to separate air exhaust lines 322 and 380 which are independently controlled by control vales 324 and 381, respectively, so that the pressure differential between the suction 'box liquid level L-301 and the separate liquid level L-304 in the drop-leg 370 may be controlled or regulated in the desired manner. In the embodiment of FIGURE 5, however, it will be noted that the gas exhaust lines 322 and 380 are connected to a common suction header 323, which would be maintained at a minimum practical operating pressure so that the minimum subatmospheric pressure may be maintained on the liquid level L404 via the control valve 324, whereas the control valve 381 leading to the second conduit means A302 would b throttled for controlling the air exhaust from above the level L301 in the suction box 300 so as to maintain the desired pressure differential while still maintaining a subatmospheric pressure above the level L-301 (of such ma nitude as to maintain the desired pressure differential across the perforated box top, not shown).

In the device of FIGURE 5 the outlet opening 325 for liquid beneath the suction box liquid level L-301 is not shown with a control valve, but a control valve of the type hereinbefore described can, of course, be employed for conventional manual operation. The control of the level L-301 is, however, maintained by controlling the air exhaust throttle valve 331. This is done by the conventional ilevel sensing means 361 in the suction box A-300 sending a signal through the signal line 360 to the control box 382 'which in turn sends a control signal such as a pneumatic signal for conventional pneumatic control of the control valve 381 through a signal line 383.

It will thus be seen that in both FIGURES 4 and 5 there is provided a suction chamber (Ar-200, A 300) having the perforate wall or box top offering restricted flow to a liquid in the stock exposed thereto and having a level L201, L-301 of liquid therein. Separate and independent means (A-202, A302 and A-201, A-301) communicate with the chambers above and below the level therein and separate and independent pressure control means 240, 381 and 224, 324, respectively, maintain the desired pressure differentials hereinbefore described.

It will be further noted that in FIGURES 4 and 5, valve means in the form of the damper 250 interposed between (or in control of) the liquid outlet 225 and the vacuum source 223, or valve means 381 interposed between the drawoff conduit A-302 and the vacuum source 223 are automatically con-trolled in response to the level sensing devices 261 and 36 1, respectively. As hereinbefore indicated, the control means or panels 259 and 382 for the valves 250 and 381, respectively, are per se conventional control devices for receiving the level sensing signal (e.g. an electric signal) and converting the same into a pneumatic signal for the control arms 258 and 383, respectively.

Referring now to FIGURE 6, it will be seen that elements shown therein corresponding to previously disclosed elements have the same reference numerals in the 400 series. In the arrangement of FIGURE 6, however, it will be seen that a multiple, selective control box 485 receives the requisite signal from the level sensing device 461 for control purposes and the control box 485 is also of conventional structure and may be selectively actuated manually or otherwise to send a pneumatic signal through the line 486 to control the valve 424, or through the line 487 to control the valve 441), or through the signal line 488 to control a pneumatic motor 489 of conventional structure that is employed for selected, controlled vertical movement of control rods 4% for a gate valve 491 in the liquid aperture 425 leading into the first drawoff conduit 420. The control circuits 486, 487 and 488 may be actuated simultaneously, in pairs or individually according to preselection of the operation of the control box 485 which may be set for actuation in response to the level sensing signal in the line 460, or as in the case of conventional control systems, the control box 435 may be used simply for manual control of signals in the control lines 486, 487 and/or 433 using a conventional instrument air pressure source indicated diagrammatically at 495, which feeds actuating air pressure into the control box 485 where it may be converted by manual regulation to the desired actuating signal.

The instant invention may also be utilized in the first stages of a press section of a paper making machine wherein suction press rolls are used to remove large amounts of Water. As illustrated in FIGURE 7, a web W is carried on a felt F through a nip defined by a plain roll 50, for example, a finished granite roll, and a suction press roll 51 having a perforated shell or cover 52. Mounted within roll 51 is a conventional suction gland 53 'seal ingly engaging an inner surface 54 of the shell 52 by means of a pair of rubber seals 56 situated on either side of the nip. An inner chamber 57 of the gland 53 is in communication with suction means (not shown) for creating a low pressure area in the suction gland to aid in drawing water through the web W, felt F and the perforated shell 52 of the press roll 51.

As is well known, water entrapped in perforations 58 formed in the shell 52 of a suction :press roll may rotate beyond the suction gland 53 without being drawn into the gland, and for this reason a saveall 59 may extend the entire width of the press roll 51 to substantially enclose the roll to catch or en-trap any water thrown out beyond the gland 53 from Water-filled perforations 58 due to centrifugal force. Usually the Water is drawn from the saveall at one end of the paper machine and the level of the liquid within the saveall is not controlled and can, in fact, vary across the width of the machine to result in paper format-ion of varying consistency.

In accordance with the principles of the present invention, a bottom wall 60 of the saveall 59 may be sloped in the direction of an opening 61 formed in a side wall 62 of the saveall. Opening 61 may be situated below a predetermined, desired level L-ll of the liquid L in the saveall, and may communicate with a draw off line or conduit indicated generally at 63 which features a conventional drop leg 64 which may lead to a dump or seal pit (not shown).

Situated at the opening 61 is an adjustable valve means for controlling the flow of liquid L into the draw olf line 63 and may comprise a vertically adjustable dam or gate 66 adapted to extend the width of the opening 61 and movable toward and away from a bottom wall 67 of the line 63 to control the flow of liquid out of the saveall 59. Vertical adjustment of the gate 66 is afforded by means of a threaded adjusting rod 68 rotatably received for vertical movement by a sleeve 69 rigidly mounted on the side wall 62. The gate 66 is connected for longitudinal movement to the rod 68 through an arm 70 which rotatably receives the rod 68 but is adapted to move vertically therewith.

Rotation of the threaded rod 68 in the complementarily threaded sleeve 69 is afforded by a hand wheel 68a.

In order to increase flow of liquid from the saveall 59 into the draw off line 63 a top exhaust line 71 connects to a top wall 72 of the line 63 and leads to a vacuum or suction header 73 which is, of course, connected to a conventional exhaust fan or pump for maintenance of a source of vacuum in line 71 as well as in an air space 74 in the draw off line 63 above the level L-2 of the liquid L. A control valve indicated diagrammatically at 76 is also provided for regulation of the vacuum in the line '71, which is, in effect, regulation of the sub-atmospheric pressure in the air space 74 in the draw oif line 63 above the liquid level LZ therein. By proper regulation of the vacuum in the air space 74, which establishes a predetermined pressure diflerential between the pressure of the air in the saveall 59 above the liquid level L1, which may be approximately atmospheric pressure, and the pressure of the air in the draw oflf line 63 above the liquid level L-2, which may be, for example, in the order of a high vacuum, and by proper regulation of the size of the opening 61 by means of the gate 66 the level of liquid in the saveall 59 can be eifectively controlled and maintained at a predetermined, desired level. If desirable, of course, the pressure of the air in the saveall above the liquid level L-l may be reduced below atmospheric pressure by maintaining the upper edges of the saveall in close runmng contact with the felt and subjecting the air in the saveall to a slight vacuum, thereby creating an air pressure in the saveall slightly below atmospheric pressure and a pressure in the draw off line 63 above the liquid level L-2 at yet a lower pressure.

FIGURE 8 illustrates an embodiment similar to that of FIGURE 1 wherein a plurality of first chambers communicate with a single second chamber and wherein parts corresponding to similar parts of FIGURE 1 are indicated by means of similar reference numerals in the 500 series. A first chamber A-5ti0 communicates with chamber A-SM which is subjected to a vacuum from the header 541. A second chamber A501 is defined by conduit 52!) and is separated from chambers A-Sllfi by means of a gate 526. Chamber A-501 is subjected to a vacuum above a liquid level L5il2 from a header 523, and liquid in conduit 520 discharges through a drop leg 521.

Reference numerals 550 and 575 indicate a plurality of conduits similar to conduit 520 and communicating liquid from a plurality of suction boxes and gates similar to those illustrated in FIGURE 8. Consequently, it is apparent that not every suction box need have a separate second chamber subjected to a vacuum, but one common second chamber A-501 can be used to accommodate a plurality of suction boxes.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. A device for regulating pressure in a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined level of liquid therein, which comprises separate and independent means communicating with said chamber above and below said level, level sensing means in said chamber and separate and independent pressure control means responsive to said level sensing means and connected to said communicating means for maintaining a first pressure differential across said perforate wall to draw liquid therethrough and a second pressure differential between said liquid level and said means communigating with said chamber below said level to drive liquid out of said chamber.

2. A device for regulating pressure in a suction chamber having a perforate wall oiiering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined level of liquid therein, which comprises separate and independent means communicating said chamber above and below said level, a source of vacuum connected to both said means, valve means interposed bet-ween one of said means and the source of vacuum, and means for controlling the valve means in response to the level in said chamber.

3. A device for regulating pressure in a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined level of liquid therein, which comprises separate and independent means communicating said chamber above and below said level, a source of vacuum connected to both said means, valve means interposed between one of said means and the source of vacuum, sensing means actuated in response to changes in the level in said chamber, and control means for the valve means actuated by said sensing means.

4. In combination, a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predeter-mined first level of liquid therein, a first conduit connected to said chamber below the liquid first level therein for drawing liquid therefrom and into a liquid pool having a second level outside said chamber, a second conduit connected to said chamber above the liquid first level therein for drawing gas therefrom, and means responsive to said chamber first level maintaining a pressure differential across said perforate wall for drawing liquid into the chamber and a pressure differential between second conduit and said pool second level for dra-wing liquid from the chamber into said pool.

5. In combination, a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined first level of liquid therein, a first conduit connected to said chamber below the liquid first level therein for drawing liquid therefrom and into a liquid pool having a second level outside said chamber, a second conduit connected to said chamber above the liquid first level therein for drawing gas therefrom, separate and independent sources of vacuum connected to each of said conduits, and valve means in each of said conduits, and means actuating one of said valve means in response to the first level in said chamber.

6. In combination, a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined first level of liquid therein, a first conduit connected to said chamber below the liquid first level therein for drawing liquid therefrom and into a liquid pool having a second level outside said chamber, a second conduit connected to said chamber above the liquid first level therein for drawing gas therefrom, separate and independent sources of vacuum connected to each of said conduits, and valve means in each of said conduits, means actuating one of said valve means, and level sensing means in the chamber controlling said actuating means in response to variations in the first level in the chamber.

7 In combination, a suction chamber having a perforate wall offering restricted flow to a liquid exposed thereto and said chamber being arranged to have a predetermined level of liquid therein, a first conduit connected to said chamber below the liquid level therein for drawing liquid therefrom and into a liquid pool having a level outside said chamber, a second conduit connected to said chamber above the liquid level therein for drawing gas therefrom and in direct gaseous communication wvith both said liquid level and the perforate wall in said chamber, separate sources of vacuum connected to each of said conduits, and valve means controlling an Opening for liquid flowing in the first conduit, said valve means maintaining liquid at said level to effect a gas seal in said chamber between said conduits.

References Cited by the Examiner UNITED STATES PATENTS 1,842,724 1/1932 Wenzel 162373 2,893,486 7/ 1959 Marti 162364 3,029,871 4/ 196 2 Hornbostel a- 162364 3,079,990 3/1963 Taylor et al 162363 FOREIGN PATENTS 690,578 4/ 1953 Great Britain.

DONALL H. SYLVESTER, Primary Examiner.

J. NEWSOME, Assistant Examiner. 

2. A DEVICE FOR REGULATING PRESSURE IN A SUCTION CHAMBER HAVING A PERFORATE WALL OFFERING RESTRICTED FLOW TO A LIQUID EXPOSED THERETO AND CHAMBER BEING ARRANGED TO HAVE A PREDETERMINED LEVEL OF LIQUID THEREIN, WHICH COMPRISES SEPARATE AND INDEPENDENT MEANS COMMUNICATING SAID CHAMBER ABOVE AND BELOW SAID LEVEL, A SOURCE OF VACUUM CONNECTED TO BOTH SAID MEANS, VALVE MEANS INTERPOSED BETWEEN ONE OF SAID MEANS AND THE SOURCE OF VACUUM, AND MEANS FOR CONTAINING THE VALVE MEANS IN RESPONSE TO THE LEVEL IN SAID CHAMBER. 